A. Field of the Invention
The present invention relates to a method of processing telephone calls where the called party is a cellular subscriber or a paging system subscriber. More particularly, the invention relates to methods of call processing to provide enhanced billing, routing, and messaging services.
B. Description of the Related Art
Cellular system subscribers typically are charged a fee for use of the cellular system, regardless of whether the cellular subscriber initiates or receives the call. Similarly, paging system subscribers are charged a fee for paging calls received. Subscribers may not have control over who calls (or pages) them, other than to keep their phone number out of the public domain. However, maintaining an unlisted number has disadvantages, and may not be practical for a business setting. Consequently, systems that require the calling party to pay, known as Calling Party Pays (CPP) and Paging Party Pays (PPP) systems, have been implemented to charge a calling party for the entire call rather than to charge the cellular/paging subscriber for calls incoming to the subscriber. That is, with CPP/PPP services, the land-line user calling a cellular or paging user will pay the land-line usage as well as the air time charges associated with the call.
After an end-user dials the cellular/paging subscriber's telephone number, the end-user is prompted with an announcement indicating they will be billed for the call. At such time, the end-user has the option of continuing the call and being billed for the call, or hanging up if they do not want to incur the charges.
The prior art systems have limited features, and are unable to charge the calling party under certain circumstances, such as when calls are initiated from payphones, hotels, etc. These are commonly referred to as "leakage calls" originating from "leakage sources."
1. The Digital Phone Network
FIG. 1 depicts a typical prior art Advanced Intelligent Network (AIN) used for call processing and routing. A calling party using telephone subscriber unit 10 conveys dialing information to its End Office 20 (EO), also known as a Service Switching Point (SSP) 20. The SSP 20 routes the call to the called party's SSP 30 that routes the call to the called party's telephone subscriber unit 40. The calling party's SSP 20 obtains the necessary information used to route the call to SSP 30 via a Signaling System 7 network (SS7), which includes a Signaling Transfer Point 50 (STP) and a Service Control Point 60 (SCP). Typically, the SCP 60 has access to an External Data Base 70 (EDB) containing various network and subscriber data. As is well known in the art, the SS7 Network is hierarchical, with the STP 50 having a routing function to direct SS7 communications to the appropriate SCP 60.
In the AIN network, call routing is performed using SS7. As is well known in the art, SS7 is generally made up of i) transport protocols known as Message Transfer Parts 1-3 (MTP) and the Signaling Connection Control Part (SCCP), and ii) user parts such as Transaction Capabilities Application Part (TCAP), Telephone User Part (TUP), and ISDN User Part (ISUP), which use the lower level MTP and SCCP capabilities. TCAP provides a way for an application at one node in the network to access a database at another node or to invoke the execution of a procedure at another node. Further information about SS7 may be found in T. Russell, "Signaling System #7," McGraw Hill (1995), the teachings of which are incorporated herein by reference.
Routing within an AIN network is performed based on dialed digits in the form of area code, exchange prefix, and line number, NPA-NXX-XXXX. The area code is referred to as a Numbered Plan Area (NPA) and the exchange prefix is referred to as NXX. The subscriber line number XXXX are digits seven through ten. Alternatively, the numbering format is often given as NXX-NXX-XXXX, where N can be any number 2-9, and X can be any number 0-9. Throughout this specification NPA-NXX will be used to refer to the area code and exchange prefix of a phone number.
In the AIN network the EO is typically a class 5 switch. The tandem switch is of class 4, meaning that switching is performed between two trunk lines and subscribers are typically not serviced directly. In the AIN network, cellular and paging service switches are typically connected to a tandem switch. The NXX numbers assigned to the cellular providers are associated, or "homed," to the class 4 tandem switches. The class-5 SSPs are configured to route cellular and paging calls directly to the tandem.
2. Calling Party Pays
In prior art CPP systems (FIG. 2), SSP 20 routes cellular (or paging) calls from the calling subscriber unit 10 to the Tandem 80 based on the dialed NPA-NXX information. Based on the called party number, tandem 80 launches a TCAP query to the SCP 60 to determine if the particular cellular or paging provider offers CPP services. In addition, the tandem queries SCP 60 using the calling party's Automatic Numbering Identifier (ANI) to determine the billable status of the calling number based on its Charge Party Station Type (CPST).
The CPST is also referred to as "ANI II." Some standard ANI II Codes are given: ANI II Code 00 is used to designate standard billable calls with no special attributes; ANI II Code 27 identifies a line connected to a pay station which uses network provided coin control signaling; ANI II Code 29 is used to identify lines serving a confinement or detention facility that are intended for inmate/detainee use and require outward call screening (e.g., 0+collect only service); ANI II Code 70 identifies a line connected to a pay station (including both coin and coinless stations) which does not use network-provided coin control signaling.
If the SCP 60 determines that the called subscriber does not have a CPP option, the SCP 60 instructs the tandem to route the call as normal to the Mobile Telephone Switching Office 90 (MTSO) for transmission to the subscriber unit 100. If, on the other hand, the SCP 60 determines that the cellular subscriber 100 (called party) has a CPP option, and the calling subscriber unit 100 is of billable status, the SCP 60 instructs the tandem 80 to route the call to the MTSO 90 and to create a billing record in an Automatic Message Accounting (AMA) data base 110 to record the charge to the calling party for the air-time associated with the call. If the SCP 60 determines that the calling subscriber 100 is not of billable status, then the SCP 60 nevertheless instructs the tandem 80 to route the call to the MTSO 90. The tandem 80 regards the call as leakage and may route the non-billable call to the MTSO 90 over a separate pre-designated trunk 120, wherein the use of that trunk indicates that the call has not been billed to the calling party. The cellular provider may then treat the call as "leakage" and not bill it, or the provider can charge the cellular subscriber for the air-time.